Sheet feeding apparatus having ultrasonic means to detect overlapping



June 7, 1966 L. J. STREET 3,254,888

lNv/ENToR LESLIE IoHN STREET Bla mow- *EJE/MM United States Patent O 3254 888 SHEET FEEDING APARATUs HAVING ULTRA- SQNIC MEANS TO DETECTOVERLAPPING Leslie John Street, Long Ashton, near Bristol, England,

assignor to Parnall 8: Sons Limited, Birmingham, England, a Britishcompany Filed July 5, 1963, Ser. No. 293,024 Claims priority,application Great Britain, July 6, 1962, 25,956/ 62 8 Claims. (Cl.271-57) This invention relates to sheet feeding apparatus, for example,of the kind wherein the sheets are fedsingly from a stack in machinesfor sorting bank checks, football pool coup-ons and the like intoreceiving stations appropriate to coded information on the sheets.

In sheet feeding apparatus of the aforesaid kind precautions are usuallytaken to avoid so far as possible the feeding of two or more overlappingsheets since such double feeding would, for example, result in thefailure of associated apparatus to read information on one or more ofthe overlapping sheets. In previously proposed feeding apparatus theseprecautions have usually taken the form of the provision of belts,wheels or the like running in the reverse direction and frictionallyand/or pneumatically engaging the opposite side of the sheets to that ofthe belts, wheels or the like which serve to frictionally and/ orpneumatically engage the individual sheets to transport the sheets fromthe stack.

`It is found in practice that despite the provision of means such as theaforesaid reverse running belts, wheels or the like it is still possibleoccasionally for two or more overlapping sheets to be fed, and thepresent invention has for its object the provision of a method and meansfor detecting the occurrence of such double feeding for initiatingappropriate action in further apparatus to which the sheets aretransported.

The invention consists of the incorporation in sheet feeding apparatusof means for detecting the feed of two or more overlapping sheetscomprising a transmitter and a receiver of longitudinal air pressurevibrations located on opposite sides of the path of feed of a sequenceof sheets, and control means for varying the output' of the transmitterand/or the sensitivity of the receiver for distinguishing between thepresence of one and two or more overlapping sheets between saidtransmitter and receiver.

The invention further resides in the meth-od of detecting the feeding oftwo or more'overlapping sheets comprising4 the adjustment of the outputand/or the sensitivity respectively of a transmitter and receiver oflongitudinal air pressure vibrations located one on each side of thepath of feed of a sequence of sheets so that the receiver senses thedifference between the presence of a single sheet and two or moreoverlapp-ing sheets between said transmitter and receiver, and utilizingthe response of the receiver to the feed of two or more overlappingsheets to initiate action in apparatus feeding and/ or receiving saidsequence of sheets.

Preferably in the aforesaid apparatus and method said longitudinal airpressure vibrations are of ultra-sonic wave length.

One example of the practical realization of the invention is describedwith reference to the accompanying drawing showing in side elevation asingle sheet feeder according to the invention in partly diagrammaticform.

The sheet feeding apparatus illustrated is designed to deliver singlesheets intermittently from a stack of sheets such as, for example, bankchecks, or football pool coupons, and comprises a magazine 10 foraccommodating a stack 11 of said sheets with the sheets disposed inparallel vertical planes also parallel with the plane of a feed3,254,888 Patented June 7, 1966 gap between the forward and reverserunning elements forming parts of sheets transporting and rejectingmeans respectively hereinafter described. Means is provided for urgingthefront face of the foremost sheet 12 of the stack into engagement withthe forward running elements 13 of the sheet transporting means forexample by supporting the magazine 12 on a conveyor belt 14 so that theconveyor urges the front partly open face of the magazine 12 towardssaid forward running elements 13.

The sheet transporting means comprises two parallel running toothedendless rubber belts 13 passing over continuously driven toothed pulleywheels 27 so that the belts follow parallel triangular courses withtheir upward vertical runs dening one side of the feed gap. The belts 13are ported in longitudinally spaced apart regions and the said verticalruns move before respective hollow shoes 15 to which are applied apartial vacuum. On the opposite side of the feed gap to the verticalruns of the belts 13 is a portedflat face 16 of a fixed sheet rejectinghead generally designated 17. Within the head 17 is disposed a drum (notshown) having ports in approximately one half of its circumference withanother part of the circumference stepped inwardly to a lesser radiusthan that of the ported sector. The ported drum sector projects througha window in the ported face 16 slightly beyond the plane of said face.The drum is continuously rotated in the opposite direction to that ofthe pulley wheels 27 and in synchrony with the movement of the belts 13.The ports in the face 116 of the rejecting head and periphery of thedrum communicate through valve ports in the drum, to a vacuum source(not shown). The aforesaid rejecting head is more fully described andclaimed in the specification of our patent application No. 269,245 filedApril l, 1963 in the United States.

Beyond the fixed head 17 the belts 13 coact with idle rollers 26,'serving to continue the feed of the sheets from the sphere of operationof the rejecting head 17 to reading and/ or sorting mechanism (notshown).

Located one on each side of the path of the intermittently fed sheets onthe horizontal runs of the belts 13 and aligned substantially normallyto the plane of said sheets is an output head 28 connected to atransmitter 29, and a receiver 30. The transmitter 29 and receiver 30consist of magneto-striction transducers generating and receivinglongitudinal air pressure vibrations preferably in the ultra-sonic rangebetween kc./sec. and 100 kc./sec. with 40 kc./sec. found to be aparticularly practical choice. However the invention is not limited tothe aforesaid wave band since both higher and lower frequencies can beemployed although in the case of frequencies below 20 kc./sec.extraneous noise can cause diiiiculty.

The assembly of transmitter and receiver may advantageously be thatmarketed by Delavan Manufacturing Company of West Des Moines, Iowa,under the name of Sonac coupler assemblies and described in DescriptiveBulletin 41-2 of Augsut 1961 published by that company.

While transducers 29 and 30 may both be located irnmediately inproximity to the path of the sheets it is more convenient to feed forexample the output from the remote transmitter 29 via a pipe 31 to thehead 28 as illustrated. Both the transmitter 29 and the receiver areconnected to an amplifier 32 incorporating a sensitivity or gain control33, and the amplifier output controls a relay 34 having output terminals35.

The relay controlled terminals 35 are connected for example to controlthe feed of the sheets to subsequent sheet processing apparatus. Forexample the opening of the circuit through the terminals 35, following adouble feed, may be used via a solenoid valve 36 connected to theterminals 35 by line 37 to vent supply conduit 38 leading to the vacuumshoes 15 to atmosphere to arrest Si further feeding from the stack 11,and to operate via a further solenoid a detlector to divert all sheetsin transit to an appropriate receptacle. Alternatively the terminals maysimply be connected to an alarm device.

In operation a stack 11 of sheets is inserted in the magazine with thesheets parallel t0 the feed gap and the front face of the foremost sheet12 urged into engagement with the upward runs of the ported belts 13. Asthe ported areas of the belts 13 reach the upper marginal part of thefront face of the foremost sheet 12 the vacuum in the shoes 15 behindthe belts 13 is communicated through the belt ports and serves to suckthe foremost sheet 12 against the belts 13 whereby the sheet 12 islifted from the stack and is transported into the region of the fixedhead 17. Shortly after the foremost sheet 12 has been gripped on thebelt 13 the vacuum is applied to the ports in the face 16 of the fixedhead and this usually serves to suck onto this face 16 any second sheetthat may be adhering to the foremost sheet 12, while allowing the firstsheet to proceed in View of the low friction between two overlappingsheets. After the upper marginal part of the foremost sheet 12 has beentransported past the fixed head and after the application of vacuum tothe fixed head ports, the vacuum is then applied to the ports in thereverse running drum so that the drum tends to return any second sheetback towards the stack 11.

Despite the operation of the aforesaid head 17 occasionally twooverlapping sheets escape past the head and proceed between thetransmitting head 28 and the receiver 30. However, in setting up themachine the sensitivity control 33 is adjusted to give an acceptance ofone thickness of the sheets, with a reasonable margin of tolerance,without operation of the relay 34, Whereas the presence of two or morethicknesses of sheets between the transmitter head 28 and receiver`30blocks transmis-sion of the ultrasonic beam and thereby is made to giverise to a loss of signal in the receiver sufficient to operate the relayso as for example to arrest further feeding and to -direct the sheets intransit to a reject station from whence they can be later taken forfurther processing.

It is to be appreciated that the above device is particularly effective-in sensing a pair of overlapping -sheets not simply due to therelatively small signal loss owing to the presence of a double thicknessof sheets between the transducers, but due to the unexpectedly largesignal loss which is found to occur at the interface between the sheets,this being important in practice since the device is thereby able toydistinguish reliably between a wide variety of single sheet thicknessesand the presence of two overlapping sheets. Further the device isinsensitive to variation in colour density of the sheets, unlikephotoelectric devices, and makes use of parts having long life.

We claim:

1. A sheet feeding apparatus incorporating means for detecting thepresence of two or more overlapping sheets of paper or the like movingalong a feed path from a feeding means adapted to normally feed saidsheets one at a time along said path comprising a transmitter and areceiver of longitudinal air pressure vibrations located on oppositesides of the path of feed of a sequence of said sheets, and controlmeans for adjusting said detector means to condition it fordistinguishing between the presence of one and two or more overlappingsheets traversing the beam of longitudinal air pressure vibrationsbetween said tran-smitter and receiver. l

2. Sheet feeding apparatus according to claim 1 wherein said transmitterand receiver operate at a frequenc above 20 kc./ sec.

3. Sheet feeding apparatus according to claim 1 wherein said transmitterand receiver operate at a frequency between 20 kc./ sec. and 100kc./sec.

4. Sheet feeding apparatus according to claim 1, wherein saidtransmitter and receiver consist of magnetostriction transducers.

5. Sheet feeding apparatus according to claim 1 wherein said controlmeans is connected to means to alter the feed of sheets when thereceiver senses two overlapping sheets.

6. A method of detecting the feeding of two or more overlapping sheetsof paper or the like comprising the adjustment of detection meansconsisting essentially of a transmitter and receiver of longitudinal airpressure vibrations located one on each side of the path of feed of asequence of sheets issuing from feed means adapted to normally feed saidsheets one at a time along said path so that the receiver senses thedifference between the presence of a single sheet and two or moreoverlapping sheets traversing the beam of longitudinal air pressurevibrations between said transmitter and receiver, and utilizing theresponse of the receiver to the feed of two or more overlapping sheetsto initiate action in apparatus handling said sequence of sheets.

7. A method according to claim 6 wherein said air vibrations have afrequency above 20 kc./sec.

8. A method according to claim 6 wherein said air vibrations have afrequency between 20 kc./sec. and kc./sec.

References lCited by the Examiner UNITED STATES PATENTS 2,063,47912/1936 Belluche 271-56 X 2,277,037 4/1942 Clark et al. 209-111.9 X2,994,528 8/1961 Hull et al. 271-56 2,999,589 9/1961 Norwich 209-111.9 X3,131,816 5/1964 Mizell et al. 209-111.9

M. HENSON WOOD, JR., Primary Examiner.

SAMUEL F. COLEMAN, Examiner.

W. F. MCCARTHY, lA. N. KNOWLES,

Assistant Examiners.

1. A SHEET FEEDING APPARATUS INCORPORATING MEANS FOR DETECTING THEPRESENCE OF TWO OR MORE OVERLAPPING SHEETS OF PAPER OR THE LIKE MOVINGALONG A FEED PATH FROM A FEEDING MEANS ADAPTED TO NORMALLY FEED SAIDSHEETS ONE AT A TIME ALONG SAID PATH COMPRISING A TRANSMITTER AND ARECEIVER OF LONGITUDINALY AIR PRESSURE VIBRATIONS LOCATED ON OPPOSITESIDES OF THE PATH OF FEED OF A SEQUENCE OF SAID SHEETS, AND CONTROLMEANS FOR ADJUSTING SAID DETECTOR MEANS TO CONDITION IT FORDISTINGUISHING BETWEEN THE PRESENCE OF ONE AND TWO OR MORE OVERLAPPINGSHEETS TRAVERSING THE BEAM OF LONGITUDINAL AIR PRESSURE VIBRATIONSBETWEEN SAID TRANSMITTER AND RECEIVER.